Enable/disable Squid. Squid configuration causes the following changes in behaviour:

The Cache-Control header is changed to allow the cache proxy to blindly cache content for a predetermined period of time (configured by $wgSquidMaxage).

The Last-Modified header is artificially shortened to ensure the cache proxy will not renew outdated HTML beyond a certain age. The Last-Modified date will never be older than $wgSquidMaxage. This will allow to refresh the cached copy in case there were changes to footer icons, sidebar, skin update, and other configuration or skin-level changes not tracked by the wiki page itself.

Purges are sent to ensure content edited by users remains up to date immediately.